Layer-specific Strain To Assess Changes Of Rabbits’ Left Ventricular Function In The Early Stage Of Acute Myocardial Ischemia

Objective To analysis longitudinal and circumferential layer-specific strain of rabbits’ left ventricular(LV)sections in the early stage of acute myocardial ischemia(AMI)using two-dimensional speckle tracking imaging(2D-STI),and to assess global and regional systolic function of LV.Methods AMI model of forty white rabbits underwent thoracotomy to ligate left ventricular branch of coronary artery was established.Two-dimensional images were recorded and stored in apical four-chamber,long-axis,two-chamber,and in the short-axis view at the level of mitral valve,papillary muscle and apex.The highest values of longitudinal strain(LS),circumferential strain(CS),global longitudinal strain(GLS)and circumferential strain(GCS),using EchoPAC,were assessed from endocardium、mid-myocardium and epicardium of eighteen sections.Results AMI model of forty white rabbits was successfully established to conduct longitudinal strain analysis,and thirty rabbits to conduct circumferential strain analysis due to ten unsuccessful sections which were refused by quality control program.①General parameters:The difference in HR between preoperative and postoperative was significant,but there was no significant difference in IVST,LVPWT,LVDd,LAD and LVEF.②Global strain:The difference in three-layer GLS,GCS,global gradient-longitudinal stain(AGLS)and global gradient-circumferential stain(△GCS)between preoperative and postoperative were significant(P<0.001)and the value was significant lower after the operation.The value of GLS and GCS were highest in endocardium and lowest in the epicardium(P<0.001),and there were significant difference between each two-layer(P<0.05).Before and after surgery,GLS and GLS were gradually decreased from the apex to the basal segment,and the difference was statistically significant(P<0.05).③Long-axis strain:The value of LS in endocardium、mid-myocardium and epicardium of left lateral、anterior and anterior septum wall all showed a great decrease(P<0.05).The value of LS in three-layer of inferior,posterior wall of left middle and apex sections were decreased after the operation(P<0.05).The value of LS in three-layer of posterior septum of basal、middle segment and inferior,posterior of basal segment were decreased,but there was no significant difference(P>0.05).④Short-axis strain:The value of CS in endocardium of left anterior,lateral,inferior wall of middle section and epicardium of anterior septum,posterior septum of basal section all showed a great decrease,and there was significant difference(P<0.05).The rest sections of CS in three-layer had no significant difference(P>0.05),but the value measured postoperative was lower than preoperative.Conclusion To analysis LS and CS layer-specific strain of rabbits’ LV sections in the early stage of AMI using 2D-STI can detailedly assess global and regional systolic function of LV.